This invention relates generally to apparatus and methods for filling containers and particularly to apparatus for aseptically filling flexible containers with food products.
The present invention is an improvement over the apparatus and method of U.S. patent application Ser. No. 343,918, filed Jan. 29, 1982, entitled Apparatus and Method for Aseptically Filling a Container and assigned to the Scholle Corporation, now U.S. Pat. No. 4,458,734, issued July 10, 1984. That application describes and claims a filling apparatus including a chamber, clamping means, cup-shaped cover, use of a sterile gas and means for sterilizing the spout and cap of a container.
Many liquid and semi-liquid products are packaged into large containers for storage and distribution to repackagers, commercial users and other users of large quantities of the products. Many of these products, particularly food products, deteriorate rapidly after exposure to oxygen. Additionally, food products must be protected against possible contamination from bacteria. Therefore, these products are often placed in large bags having, for example, a five gallon capacity, made of plastic or similar flexible material and having one spout through which the bag is filled and from which the product may be dispensed from the bag. These bags are advantageous in that as the product is dispensed from the container, the bag collapses around the remaining material so that no air enters the container. With containers of a fixed shape or internal volume, air must enter the container to fill the volume left in the container as the product is dispensed. Air contains oxygen and frequently carries harmful bacteria into such containers. These containers typically have a rigid or semi-rigid plastic spout through which the product passes to enter or leave the container.
Care must be taken in packaging food products into the containers to prevent bacteria that could create a potential health risk to the consumer of the food product from entering the container. To ensure sterility, the containers are filled using a chamber that maintains a sterile atmosphere around the spout of the container. Typically, a sterile chamber is filled with a sterile gas, with the gas being maintained in the chamber at pressure greater than the ambient pressure. The pressure of the gas in the chamber ensures that very little air from outside the chamber enters the chamber, since the gas flow through any opening in the chamber walls is predominantly from the higher pressure interior to the lower pressure exterior. An opening in the bottom of the chamber receives the spout of one of the plastic bag food containers. Once the spout is placed in the opening, the spout is brought into contact with a filling head inside the chamber, and the product is dispensed into the bag.
Because of the pressure maintained in the chamber, a substantial amount of the gas may escape through the opening, particularly between filling operations after the spout of one container has been removed from the opening and before another has replaced it. Additionally, since the opening must be slightly larger than the spout of the containers, when the spout is in the opening, the gap between the spout and the rim of the opening permits the gas inside the chamber to escape to the outside environment. Because such a large amount of the sterile gas is lost in this way, a number of problems have existed. One of these problems is that only a relatively inexpensive gas can be practically used in the chamber, thereby effectively limiting the choice of gases to just one gas: hot sterile air. However, use of sterile air, which contains oxygen, exposes the food product to oxygen during the filling operation, which reduces the shelf life of the food product. Also, since the sterile gas must be kept hot to ensure continued sterility of the chamber, large volumes of the gas must be heated, which consumes a large amount of energy and requires the use of a considerable amount of equipment.
Thus, a need has existed for an apparatus for filling food containers that uses only a small amount of sterile gas, so that a gas which is inert with respect to the food products could be used as the sterile gas to increase the shelf life of the product being packaged, and to substantially reduce the heating requirements for the gas.